PURPOSE: The purpose of this study was to determine the effects of exercise program on cardiopulmonary functions and shoulder joint functioning in breast cancer patients who under- went radiation therapy after surgery. METHOD: Subjects in the experimental group(N=12) participated in an exercise program for eight weeks. The Exercise program consisted of shoulder stretching, arm weight training, and walking on treadmill. Maximal oxygen uptake(o2max), maximal running time, shoulder joint range of motion, and shoulder functional assessment were determined before and after the exercise program. Baseline sociodemographic and medical data were compared between experimental group and control group using the Fisher's exact test and Mann- Whitney U test. For effects of the exercise program, repeated measures ANOVA were used. RESULT: 1) Following the exercise program for eight weeks, both o2 max and maximal running time tended to increase in experimental group comparing with the control group. 2) Shoulder abduction, extension and flexion of the operated upper extremity in the experimental group comparing with control significantly increased after the exercise program(p<0.05). 3) Shoulder flexion of the normal upper extremity in the experimental group comparing with control significantly increased after the exercise program(p<0.05). CONCLUSION: The results suggest that the exercise program for breast cancer patients undergoing radiation therapy after breast surgery can improve shoulder functions and increase cardiopulmonary functions, which are maximal oxygen uptake and maximal running time.